1. Field of the Invention
The present invention generally relates to a heartbeat synchronous pulse wave detecting apparatus and particularly to such an apparatus which correctly identifies proper upper and lower peaks of the pulse wave.
2. Problem Solved by the Invention
There is known a heartbeat synchronous pulse wave detecting apparatus having a probe which is adapted to be set on a body surface of a subject to sense a pulse wave transmitted thereto in synchronous relationship with heartbeats of the subject and generates a signal representative of the sensed heartbeat synchronous pulse wave. An arterial pulse wave detecting apparatus is one of such apparatus. As shown in FIG. 8, a heartbeat synchronous pulse wave, such as an arterial pulse wave, consists of successive pulses each of which corresponds to a heartbeat, and each pulse normally has proper (or primary) upper and lower peaks (A, D) and in addition a secondary upper peak (C) and a secondary lower peak or notch (B). The proper upper peak corresponds to the systole (or compression) of the heart, while the proper lower peak corresponds to the diastole (expansion). Those peaks periodically occur in the order of A, B, C, D, A, B, C . . .
The conventional apparatus is capable of determining upper and lower peaks of a heartbeat synchronous pulse wave. However, it suffers from a problem that it erroneously determines a secondary upper peak as a proper upper peak, and/or a notch as a proper lower peak. For example, in the event that the magnitude of a secondary upper peak is greater than that of a proper upper peak, the conventional apparatus confuses the secondary upper peak with the proper upper peak and erroneously determines the secondary upper peak as the proper upper peak.